Which Donald Trump Will Chart the U.S. Course in Afghanistan?

U.S. President Donald Trump probably does not relish taking on a problem like the conflict in Afghanistan. It is a “wicked” problem, intricate and almost incomprehensibly complex, with a large and growing cast of participants playing a role or at least having a stake. Inside Afghanistan there is a mesh of actors with clashing, often incompatible goals. Outside the country a solution depends on Pakistan, which deeply fears India and has its own growing jihadi problem. Russia and the self-styled Islamic State, while late to the conflict, are now involved and muddling things even further.

But despite all this, Trump must frame a strategy: In statecraft, a problem ignored seldom simply goes away. ...